There are four classes of catalytic membrane reactors, based on their topological configurations. The first class, called a perma-selective wall membrane reactor, has a semi-permeable membrane to transport a product or reactant while confining a bulk or homogeneous catalyst behind the membrane. The second class, called a tea-bag reactor, has a catalyst sandwiched between two membranes. The third class, called a membrane confined catalytic reactor, has a catalyst in the interior of a membrane. Reactions are catalyzed and products are formed as reactants flow through the interior of the membrane. The fourth class, called a surface catalyzed membrane reactor, has a single catalytic layer which forms the non-porous membrane or which is attached to the surface of a non-porous membrane structure to induce reactions that form products at the exterior surface of the catalytic layer. It is this latter class with which the present invention is concerned.
Single layer surface catalyzed membranes have been primarily used for hydrogenation and dehydrogenation reactions. See, for example, Zelyaeva et al., Khim. Tekhnol., 22(6), 684-7 (1979), which discloses the use of pure metal films (usually Pd foils) in hydrogenation and dehydrogenation reactions. An advantage of such a system derives from the spatial separation of the catalytically important functions of bond activation and activated species transport. Unfortunately, reaction rates for such membranes are quite low due to the limited permeability of the thick (20-1,000 micron) films employed to transport hydrogen. In this regard, see Zhernosek et al., Kinet. Katal., 20(4), 921-4 (1979). Thus, it is an object of the present invention to provide a surface catalyzed membrane that has improved transport properties.